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BMS Tropical Update 9/25/2017 12 PM CDT

Maria is weakening at a greater pace than previously thought, and it will now likely have little impact on the insurance industry as it stays a safe distance from land and begins to race across the Atlantic on Wednesday. This is great news and should provide the insurance industry with a much needed break before the next area of tropical trouble shows up in the southwest Caribbean late next week.

Maria Final Forecast
Today’s main weather story continues to be Maria which is a weak Category 1 hurricane 315 miles southeast of Cape Hatteras, NC.  She is moving north at a slow 7 mph  towards the North Carolina coast. Satellite imagery shows Maria’s inner core being ripped apart by dry air and wind shear. A large, cloudless area now exists where you’d typically expect intense thunderstorm activity to be. Dry air being forced into Maria’s inner core by strong winds aloft (wind shear) is the culprit, and its weakening influence won’t let up anytime soon.

Notice the lack of deep convection on in the center of Maria and on the west side of the center.

Another factor, as discussed yesterday, is that Maria is tracking over the cold wake of Hurricane Jose, which has also clearly helped in Maria’s deterioration.

Sea Surface Temperatures off the North Carolina are below 26 degrees C (78.8 F) which is not conducive of tropical convection. This is a direct result of the cold wake left from Hurricane Jose last week. Over the next 12 hours Maria will be moving over this colder water which will further weaken Maria into a tropical storm.

The confidence in Maria’s track forecast continues to improve with there now being very little probability of landfall (less than 20%). However, a weakening ridge of high pressure over New England will guide Maria close enough to the Outer Banks that I expect some of these coastal communities could see tropical storm-force winds (40+ mph). However, with Maria rapidly falling apart, it is also very possible that these conditions will not be experienced. The biggest hazard at this time is the strong onshore wind that will pile up water on the ocean side of the northern Outer Banks and on the bay side of the southern Outer Banks. Storm surge of a couple feet in both of these areas is expected. Maria’s impact should be limited to the coastal areas, however, as the inland areas of North Carolina likely won’t even see rain over the next few days.  At this time I don’t expect that Maria to cause enough PCS loss for North Carolina to be designated as a loss state, but her Puerto Rico impacts have already placed her in the record books.

As Maria moves slowly northward, it will continue to weaken and perhaps even stall just east of the Outer Banks as the steering currents weaken. An approaching upper level trough that is currently moving across the central plain states should then shoot the storm rapidly out to sea at the end of this week.

Next Tropical Trouble
The southwest Caribbean certainly seems to be the next area to watch for tropical development. The following is a look at the ECMWF Probability of Tropical Depression formation for Thursday, October 5.

The long range ECMWF ensemble are sniffing out a general area low pressure in the Western Caribbean Sea late next week.

In the meantime, enjoy the lull in tropical activity. I’ll provide new updates if I feel there is any threat to the insurance industry.

BMS Tropical Update 9/24/2017 10 AM CDT

Maria Still Has A U.S. Landfall Threat

I just wanted to provide a quick weekend update on Hurricane Maria and discuss the final end game that will play out this week as it slowly tracks northeast of the Bahamas.  Maria is currently located 300 miles northeast of Great Abaco Island and moving north at 9 mph as a Category 2 hurricane.  Maria is expected to maintain a north to northwest direction of travel until Wednesday of this week.  As suggested in my last update, the National Hurricane Center’s (NHC) cone of uncertainty has expanded to cover the Outer Banks of North Carolina, which means a U.S. landfall is still possible.

Track Guidance

Although the NHC cone of uncertainty is highlighting the risk of landfall along the North Carolina coastline, it seems that there is a 50/50 split in the number of ensemble members from the GFS and ECMWF that have Maria making landfall as opposed to not making landfall.  The landfall probability is currently as high as 50%.  As I mentioned back on September 18th, the end game forecast for Maria would be complicated due to Hurricane Jose, which has now dissipated into open ocean 200 miles southeast of Nantucket, Massachusetts.  Jose has no doubt spared the U.S. from yet another major hurricane landfall this season.

 

 Ensemble Guidance

The ensemble guidance below has been trending to the west with a higher and higher likelihood of landfall.   This trend needs to be watched carefully for a possible landfall on Wednesday this week.  However, after Wednesday, a large scale upper level trough is expected to push Maria out across the north Atlantic.

 

GFS (American) ensemble forecast showing a 40% chance that Maria could track over the Outer Banks of NC before a sharp right turn out to sea.

 

ECMWF (European) ensemble forecast showing several forecasts that track inland to North Carolina before a sharp right turn out to sea. Currently there is a 60% chance of landfall along the Outer Banks.

Intensity

As mentioned, Jose likely has steered Maria away from a southeast U.S. landfall as a major hurricane.  Jose’s slow track will likely also help in decreasing Maria’s intensity later this week, as Maria is expected to follow a similar track to Jose over cooler waters.  Jose has also caused upwelling in these waters, and this is making it more difficult for Maria to maintain its intensity.  I expect fluctuations in Maria’s intensity over the next 36 hours until it reaches some of that colder water.  Also, around Wednesday of this week, wind shear should start to increase from the upper level trough, which should decrease Maria’s intensity.  At this time, I expect Maria to only be a Category 1 hurricane as it moves toward the North Carolina coastline on Wednesday of this week.   It should be noted, however, that Maria is a large cyclone and the associated tropical storm-force winds could eventually reach the North Carolina coastline even if Maria does not make landfall.  It should also be noted that the strongest winds will be on the right side of the storm as it tracks towards North Carolina, so those winds would likely stay off shore.

Insured Loss

A few worst-case scenarios at this time might be Alex 2004 (which did not trigger a PCS Event) and Ophelia 2005, which triggered a $35 million insured loss event.  More recently in 2014, Arthur made landfall on the Outer Banks as a Category 2 hurricane.  Arthur is also the first Category 2 hurricane to make landfall in the U.S. and not be registered as a PCS insured loss event.  At this stage, it’s difficult to understand what type of insured losses to expect from Maria if it tracks close enough to the North Carolina coastline.  Given the current forecast, it should be expected that tropical storm-force winds may be experienced along coastal sections.  Hurricane conditions may be experienced on the Outer Banks, but this will depend on how close Maria tracks to the Outer Banks.  However, as noted above, the strongest winds would still be to the right of the storm center and away from the coastline.  I do expect some areas of the Outer Banks to experience storm surge of up to 8 feet, which could flood some parts of the Outer Banks.

Expected storm surge at Duck Pier, NC showing a storm surge as high as 6 feet.

Next Tropical Troubles

It is that time of year where the African originated storms shut down, and given the current surge of dust off Africa, this seems to likely be the case for at least the near future.

Dust and dry air off Africa now dominate the region

Without any new named storm development since September 16th and with Maria expected to dissipate out to sea later this week after a close interaction with the North Carolina coast, we will have a lull in this very busy season.  Even the busy 2005 hurricane season had a lull, so this season is likely not done yet.  I expect the next area of tropical trouble to develop off the Central American coastline in the western Caribbean later next week, maybe around October 6th.

ECMWF Normalized sea level pressure forecast valid for October 2nd showing Maria off the coast of Nova Scotia, and possible new development off the coastline of Honduras and Nicaragua.

This is one of the very few areas that has not seen tropical activity this season.  The waters here are very warm and the wind shear is low, so the conditions are ripe for more tropical trouble here yet this season.

Current Sea Surface Temperature Anomaly Not the normal to colder than normal along the southeast coastline.

In the meantime, enjoy the lull in this 2017 Atlantic Hurricane Season once Maria turns out to sea later this week .

BMS Tropical Update 9/20/2017 4 PM CDT

2017 Atlantic Hurricane Season Records Continue To Fall

The 2017 Atlantic hurricane season, which has already been memorable, continues to create long-lasting memories which will likely be talked about for decades. The newest talking point is Maria’s landfall at 6:35 this morning near Yabucoa, Puerto Rico. Maria arrived as a top end major Category 4 hurricane with maximum sustained winds of 155 mph and a pressure of 917 mb. Maria will likely be the strongest storm in terms of pressure to make landfall in Puerto Rico since 1928 – in terms of wind, it’s the second strongest. It is also the third most intense (by pressure) U.S. hurricane on record to make landfall behind Hurricane Camille, and the  Labor Day 1935 hurricane.

The statistics and images coming out of Puerto Rico indicate that Maria will likely be one of the largest natural catastrophes the island has ever experienced in terms of insured loss. But, I won’t dive into the devastation that has already occurred on the island, which is being covered extensively, but rather focus on the uncertainty of Maria’s long-term impact on the U.S. mainland.

Maria’s U.S. Mainland Threat

The geography of Puerto Rico has had a tremendous impact on Maria’s current intensity. The infrared satellite imagery above shows that the storm’s interaction with the high mountains has resulted in weakening, with a clear eye no longer visible. Unfortunately, this makes the storm no less dangerous, as winds well over 100 mph continue to beat the island. Torrential rainfall will remain as well, with totals nearing two feet in the higher terrain. Flash flooding and mudslides will be major issues for the next few days as Maria begins to move away from the island.

As Maria moves today toward the northwest, this weakening could influence the future track of the storm over the next week which, at this point, is still uncertain. A wobble south toward Hispaniola would result in a weaker system that may allow for a track farther west in the long term. The current forecast track takes the storm just north of Hispaniola, where the effect of land interaction would be minimal, thus keeping Maria on a more northwest track away from the East Coast of the U.S. next week.

The other complicating factor is the continued influence of Tropical Storm Jose, as discussed in my Monday update. Jose has already been a named storm for 15 days, which ties it for the 10th longest named storm since the beginning of the satellite era. Jose is still a large storm and, if it were not for Maria, would be a front-page news story. However, as I previously suggested, its insured impact has been minimal and similar to that of a nor’easter.

Currently Jose is doing another small loop off the New England coastline and is expected to continue to weaken over colder water as it moves back to the west later this week.

Reposting this image as the general ideas still holds from Monday thinking on overall pattern driving the northward turn of Maria.

Maria is expected to follow this weakness in the upper level ridge that Jose has created. However, the exact movement is a bit uncertain based on Maria’s trajectory away from Hispaniola and how far west Jose actually tracks. The general model guidance currently keeps Maria away from the East Coast. I do, however, expect the western edge of the National Hurricane Center’s cone of uncertainty to be very close to the coastline of North Carolina and Massachusetts as the five-day forecast cone expands northward over the next few days.

Right now, the forecast models have a bias that sometimes curve hurricanes northward  moving the hurricane to the northeast. If there is an error, it would result in a greater correction to the west with each model run.

Current long range track ensemble guidance from the American (GFS) and European (ECMWF) models. Most ensemble members keep Maria off the East Coast of the U.S. Some members however offer up landfall options all along the Northeast Coast of the U.S.

Currently, there is a 30% chance of U.S. landfall in New England per the American(GFS) ensemble model and a lower 10% chance from the ECMWF ensemble model. It should be noted, however, that cooler water temperatures and increasing wind shear will result in weakening of Maria as the storm moves northwest and then north this weekend. It would likely only be a Category 1 hurricane north of North Carolina.

Next Area Of Tropical Troubles

This is the next area to watch. This is the forecast valid for Oct 6th suggesting low pressure will be across the Western Caribbean

The next area to watch will be the western Caribbean, as the longer range models are suggesting tropical cyclogenesis in early October.

BMS Tropical Update 9/18/2017 12 PM CDT

Although there are no current threats to the U.S. mainland, I would like to provide a brief update on the thoughts that were discussed in Friday’s Tropical Update.

Below are a few key points about each tropical system:

Tropical Depression (TD) Lee:
TD Lee is currently 1060 miles west of the Cabo Verde Islands and is a weak tropical depression. It has weakened significantly since being named a tropical storm on Saturday morning and is now battling dry air and wind shear. Lee is expected to dissipate over the next 24 hours and will not likely be a threat to the insurance industry.

Hurricane Jose
Jose is currently 265 miles east-southeast of Cape Hatteras, NC and is moving north at 9 mph. It is currently a Category 1 hurricane.

Jose continues to show signs of weakening on satellite imagery as dry air is wrapped into the circulation. It will likely continue to weaken as it moves over increasingly cold water, as discussed on Friday. It should turn into a subtropical system later this week.

The outer bands of Jose will arrive on the coast between Boston and Cape Hatteras on Tuesday morning. These bands will feature breezy conditions and light/moderate rain. Overall, there should be minimal impact on Tuesday as rain bands continue to rotate onshore.

The one area of concern that’s been a given since the beginning loop early last week are the large waves that will continue to pound all ocean facing beaches in Delaware, New Jersey, Long Island, Rhode Island, and Massachusetts. Beach erosion will be an issue for the typically at-risk areas. Additionally, astronomically high tides will fuel coastal flooding concerns for low-lying areas as persistent onshore winds push a slight storm surge into eastern Massachusetts and the Long Island Sound. Waves and surge will gradually subside on Thursday as the storm weakens.

Beyond Thursday, Jose will become trapped between two upper level systems. As a result, it will linger off the New England coast as it weakens due to the cold waters in the region. In the long range, there is a chance that its remnant moisture could loop around back into coastal New England and play a role in Maria’s long-term forecast, as discussed in more detail below.
At this time, the threat of major insured loss from Jose is low.

Hurricane Maria

Hurricane Maria, which was Invest 96L when discussed on Friday, was my biggest concern due to its track toward the Windward Islands. It is now 60 miles east of Martinique as a Major Category 3 with sustained winds of 120 mph.  Rapid intensification is still expected today and it looks like Maria could have a small eye suggesting a tight central core with very strong winds.

These continued signs of intensification are likely due to  warm waters not affected by Irma up-welling.  Richard Dixon @catinsight has put together a nice little graphic showing that there is currently little overlap across the Caribbean islands between the hurricane-force winds from Hurricane Irma and the forecasted wind swath for Maria. The overlap could occur near Puerto Rico, which will likely be impacted by Maria as a major hurricane on Wednesday of this week.


In the long range forecast, Maria still has some uncertainty not only in intensity but also with its future track. These go hand and hand. There is a chance that Maria could be weakened by the high topography of Puerto Rico, depending on its track over the island. Parts of the various ensemble model guidance from last night showed Maria moving west and dissipating over the high mountains of Hispaniola and Southern Cuba. Some model guidance also points to a Florida landfall or potentially even a track into the Gulf of Mexico. Many more ensemble members point Maria up the eastern seaboard, with impacts spreading all the way to the mid-Atlantic. Finally, the storm could recurve out to sea before impacting land. So, which of these scenarios is most likely in the long range?

All the ensemble runs from last night showing all the possible tracks for Maria. Currently there is only a 5-10% of landfall given the ensembles Map provided by Allan Huffman and models.americanwx.com

To understand that question we need to look at the bigger atmospheric pattern. The upper level forecast map from the ECMWF for Thursday shows a complex and highly amplified pattern over North America.

ECMWF forecast for this Saturday with highlights of the different features that will determine Maria’s future track.

The jet stream will be in what’s called a meridional flow pattern with high amplitude waves. This pattern is being driven by the recurvature of Typhoon Talim, which was previously discussed, and tends to cause a trough of low pressure to form along the East Coast 6-10 days later. However, it would appear that the blocking high pressure over the Great Lakes will attempt to stay in place. Jose will stand in the way from the high building back to the East. Therefore, this will likely create a weakness in the ridge. How quickly Jose can either leave the scene or weaken will have a huge impact on how quickly the ridge can rebuild, and thus will play a role in Maria’s track over the long range.

It appears at this point that Jose will be around until this weekend, which should attract Maria up to the east of the Bahamas. Maria will likely follow the path of least resistance around the Bermuda high and the weakness Jose has produced within the high pressure along the western part of the Atlantic Ocean. This would keep Maria away from the U.S. coastline. Although it currently looks like Maria will stay away from East Coast of the U.S., there is still some uncertainty in the long range. The overall forecast pattern is complex with several moving puzzle pieces that will come together later this week.

The insured impact from Maria will be high in the short-term as it will be a major hurricane when it interacts with some of the Caribbean islands yet to see impacts this year. Puerto Rico will likely take a direct hit from Maria.  The last such major hurricane was Hurricane Hugo 1989.


The insured impact in the long-term is unknown at this time, given the uncertainty in the forecast.  Currently there is only a 5 – 10% chance Maria would make U.S. landfall given the current ensemble forecasts.

Other Tropical Troubles

There is nothing else to worry about at this time off the coast of Africa.  Lots of dust and dry air and little convection over Africa.

Current Dust Layer from http://tropic.ssec.wisc.edu/

The next tropical development could occur near the coast of central America later next week, but this is with low confidence and little model support in the long range. However, this is an area to watch as October approaches, when the Main Development Region (MDR) tends to shut down and new named storm development tends to form in the western Caribbean as climatology suggests below.

Source: http://www.nhc.noaa.gov/climo/